<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div {
            width: 300px;
            height: 300px;
            background-color: pink;
            /*dashed    虚线*/
            /*solid     实线*/
            /*dotted    点线*/
            border-bottom: 10px dashed red;
        }
    </style>
</head>
<body>
<div>内容</div>
</body>
</html>